Fan blade retainer

Abstract

A rotor blade retention assembly includes a rotor blade having a dovetail mounted in a complementary axial dovetail groove in a rotor disk. A primary blade retainer retains the blade in the groove against axial movement in a first direction. A secondary blade retainer retains the blade in the groove after a predetermined travel of the blade in the first direction upon failure of the primary blade retainer to restrain the predetermined travel.

Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims; I claim: 
     
       1. A retention assembly for a rotor blade comprising: a rotor disk having a pair of circumferentially spaced apart dovetail posts defining therebetween an axially extending dovetail groove;   said rotor blade having a dovetail being complementary to said dovetail groove and disposed therein for radial retention by said posts;   a primary blade retainer fixedly joined to said disk for retaining said blade in said groove against axial movement in a first direction; and   secondary means disposed in said groove and cooperating with said dovetail for wedging said blade in said groove after a predetermined axial travel of said blade in said first direction upon failure of said primary blade retainer to restrain said predetermined travel.   
     
     
       2. An assembly according to claim 1 wherein said secondary means comprise: said dovetail including a radially inwardly facing base having a first wedge inclined radially inwardly therefrom at a first inclination angle; and   an elongate spacer having a proximal end fixedly joined to said disk, and a second wedge disposed in said groove radially between said dovetail and said disk, said second wedge being inclined radially inwardly at a second inclination angle and being spaced axially from said first wedge in said first direction to define a predetermined gap therebetween for allowing said predetermined travel of said blade in said first direction upon failure of said primary blade retainer after which said first wedge engages said second wedge for restraining further axial movement of said blade in said groove in said first direction.   
     
     
       3. An assembly according to claim 2 wherein said first and second inclination angles are substantially equal, and said first and second wedges are substantially parallel to each other. 
     
     
       4. An assembly according to claim 3 wherein said first and second inclination angles are acute angles selected for generating a radial wedge force between said first and second wedges for wedging said dovetail against said posts to generate friction force against travel of said blade in said first direction. 
     
     
       5. An assembly according to claim 4 wherein said first and second inclination angles have values up to about 10°. 
     
     
       6. An assembly according to claim 4 wherein said primary blade retainer comprises: a retention plate fixedly joined to said dovetail posts, and fixedly joined to said spacer proximal end;   a crushable pad disposed between said retention plate and said dovetail for restraining axial movement of said blade in said groove; and   said pad having an axial width greater than said predetermined gap for allowing said first and second wedges to engage each other upon a predetermined amount of crushing of said pad.   
     
     
       7. An assembly according to claim 4 wherein: said first direction is an axially upstream direction;   said dovetail has a forward end facing in said axially upstream direction, and an aft end facing in an axially downstream direction; and   said first and second wedges are disposed adjacent to said dovetail aft end.   
     
     
       8. An assembly according to claim 4 wherein: said first direction is an axially upstream direction;   said dovetail has a forward end facing in said axially upstream direction, and an aft end facing in an axially downstream direction; and   said first and second wedges are disposed adjacent to said dovetail forward end.   
     
     
       9. An assembly according to claim 4 wherein said spacer is formed of an extrudible material for dissipating energy by extrusion thereof upon engagement of said first wedge with said second wedge and travel in said first direction.